This invention relates to an improvement of a steering switch pad apparatus, and more particularly to an apparatus of the type having a power transmission mechanism for associating a steering column side to a steering pad including switches such as push button switches and display indication in such a manner as to keep the steering pad standstill even when the sterring wheel is rotated so that difficulties in operating switches and seeing the display indication due to the rotation of the steering pad together with the steering wheel can be prevented.
Heretofore, there is known a steering switch pad apparatus having a power transmission mechanism of this type as shown in FIGS. 1 and 2.
In the drawings, a steering shaft 1 is provided with a boss 3 which is fixedly attached to a boss plate 2a of a steering wheel 2. Said boss 3 is fastened to the steering shaft 1 by a nut 4. A pad base 7 of a steering pad 6 having push botton switches 5 and display thereon is rotatably fitted on the boss 3 and a C-ring 8 is provided in order to prevent the pad base 7 from coming off.
At more than two places in the steering column side, fixing pins 9 having slant surfaces 9a at the foremost end portions are reciprocatably received by pin holders 10. A spring 11 is stretched between each of the fixing pins 9 and pin holders 10, so that the fixing pin 9 is biased toward the pad base 7.
The pad base 7 is formed with a recess 7a in the position opposite to the pin holder 10. The foremost end portion of the fixing pin 9 is fitted in said recess 7a. Because of said fitting, rotation of the steering pad 6 is prevented.
The boss plate 2a is designed such as to be rotated traversing the fixing pin 9. The boss plate 2a is formed with a slant surface 2b at the portion which contacts the fixing pin 9, so that when the boss plate 2a hits the fixing pin 9, the fixing pin 9 can be easily pushed into the pin holder 10 through the slant surface 9a thereof.
Because of the above arrangement, when the fixing pin 9 is pushed into the pin holder 10 by the boss plate 2a, the steering wheel 2 becomes rotatable through that portion. However, since at least one of the fixing pins 9 are fitted in the recesses 7a of the pad base 7 at other portions, the steering pad 6 is normally kept standstill, even when the steering wheel 2 rotates.
Although the steering pad 6 is not rotated and kept standstill as mentioned above, everytime the boss plates 2a traverses the fixing pin 9 during the rotation of the steering wheel 2, the fixing pin 9 is urged to hit the pad base 7 due to the force of the spring 11. Therefore, such inconveniences as that hitting impact is transmitted to the driver, hitting sound is generated and that an unpleasant feeling is created since the rotary loads of the steering wheel 2 are increased everytime the slant surface 2b of the boss plate 2a hits the slant surface 9a of the fixing pin 9 are resulted, thereby jeopardizing smooth operation of the steering wheel.
The present invention is accomplished in order to remove the above disadvantages.